13591856538 has 112 divisors (see below), whose sum is σ = 33810503496. Its totient is φ = 4068869760.

The previous prime is 13591856533. The next prime is 13591856557. The reversal of 13591856538 is 83565819531.

13591856538 is a `hidden beast` number, since 1 + 3 + 59 + 1 + 8 + 56 + 538 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 12976171569 + 615684969 = 113913^2 + 24813^2 .

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (13591856533) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 691608 + ... + 710988.

Almost surely, 2^13591856538 is an apocalyptic number.

13591856538 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 13591856538, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16905251748).

13591856538 is an abundant number, since it is smaller than the sum of its proper divisors (20218646958).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

13591856538 is a wasteful number, since it uses less digits than its factorization.

13591856538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19451 (or 19436 counting only the distinct ones).

The product of its digits is 3888000, while the sum is 54.

The spelling of 13591856538 in words is "thirteen billion, five hundred ninety-one million, eight hundred fifty-six thousand, five hundred thirty-eight".